feat: import and render document-level background

packages/layout-engine/contracts/src/index.ts

@@ -835,6 +835,11 @@ export type PageMargins = {
   gutter?: number;
 };
 
+export type DocumentBackground = {
+  /** Solid page background color as a CSS hex value. */
+  color: string;
+};
+
 export type ImageBlockAttrs = {
   sdt?: SdtMetadata;
   containerSdt?: SdtMetadata;
@@ -2298,6 +2303,8 @@ export type HeaderFooterLayout = {
 export type Layout = {
   pageSize: { w: number; h: number };
   pages: Page[];
+  /** Optional document-level page background from OOXML w:background. */
+  documentBackground?: DocumentBackground;
   columns?: ColumnLayout;
   headerFooter?: Partial<Record<HeaderFooterType, HeaderFooterLayout>>;
   /**

packages/layout-engine/contracts/src/resolved-layout.ts

@@ -1,6 +1,7 @@
 import type {
   ColumnLayout,
   ColumnRegion,
+  DocumentBackground,
   DrawingBlock,
   FlowMode,
   Fragment,
@@ -32,6 +33,8 @@ export type ResolvedLayout = {
   blockVersions?: Record<string, string>;
   /** Resolved pages with normalized dimensions. */
   pages: ResolvedPage[];
+  /** Optional document-level page background from OOXML w:background. */
+  documentBackground?: DocumentBackground;
   /** Document epoch identifier from the source layout. Used for change tracking in the painter. */
   layoutEpoch?: number;
 };

packages/layout-engine/layout-engine/src/index.ts

@@ -28,6 +28,7 @@ import type {
   SectionNumbering,
   FlowMode,
   NormalizedColumnLayout,
+  DocumentBackground,
   HeaderFooterResolutionSection,
 } from '@superdoc/contracts';
 import {
@@ -463,6 +464,7 @@ function calculateChainHeight(
 export type LayoutOptions = {
   pageSize?: PageSize;
   margins?: Margins;
+  documentBackground?: DocumentBackground;
   columns?: ColumnLayout;
   flowMode?: FlowMode;
   semantic?: {
@@ -3199,6 +3201,7 @@ export function layoutDocument(blocks: FlowBlock[], measures: Measure[], options
   return {
     pageSize,
     pages,
+    ...(options.documentBackground ? { documentBackground: options.documentBackground } : {}),
     // Note: columns here reflects the effective default for subsequent pages
     // after processing sections. Page/region-specific column changes are encoded
     // implicitly via fragment positions. Consumers should not assume this is

packages/layout-engine/layout-resolved/src/resolveLayout.ts

@@ -345,6 +345,7 @@ export function resolveLayout(input: ResolveLayoutInput): ResolvedLayout {
     flowMode,
     pageGap: layout.pageGap ?? 0,
     pages,
+    ...(layout.documentBackground ? { documentBackground: layout.documentBackground } : {}),
   };
 
   if (blocks.length > 0) {

packages/layout-engine/painters/dom/src/index.test.ts

@@ -432,6 +432,26 @@ describe('DomPainter', () => {
     expect(fragment.textContent).toContain('world');
   });
 
+  it('paints document-level page background from resolved layout', () => {
+    const painter = createTestPainter({ blocks: [block], measures: [measure] });
+    painter.paint({ ...layout, documentBackground: { color: '#EEEEEE' } }, mount);
+
+    const page = mount.querySelector('.superdoc-page') as HTMLElement;
+    expectCssColor(page.style.background, '#EEEEEE');
+  });
+
+  it('keeps the configured page background when no document background is present', () => {
+    const painter = createTestPainter({
+      blocks: [block],
+      measures: [measure],
+      pageStyles: { background: '#FFFFFF' },
+    });
+    painter.paint(layout, mount);
+
+    const page = mount.querySelector('.superdoc-page') as HTMLElement;
+    expectCssColor(page.style.background, '#FFFFFF');
+  });
+
   it('applies paragraph alignment to line elements', () => {
     const alignedBlock: FlowBlock = {
       kind: 'paragraph',

packages/layout-engine/painters/dom/src/renderer.ts

@@ -1281,18 +1281,19 @@ export class DomPainter {
     this.beginPaintSnapshot(resolvedLayout);
 
     this.totalPages = resolvedLayout.pages.length;
+    const previousLayout = this.currentLayout;
+    this.currentLayout = resolvedLayout;
     if (this.isSemanticFlow) {
       // Semantic mode always renders as a single continuous surface.
       applyStyles(mount, containerStyles);
       mount.style.gap = '0px';
       mount.style.alignItems = 'stretch';
-      if (!this.currentLayout || this.pageStates.length === 0) {
+      if (!previousLayout || this.pageStates.length === 0) {
         this.fullRender(resolvedLayout);
       } else {
         this.patchLayout(resolvedLayout);
       }
       this.setMountedPageIndices(this.createAllPageIndices(resolvedLayout.pages.length));
-      this.currentLayout = resolvedLayout;
       this.changedBlocks.clear();
       this.currentMapping = null;
       return;
@@ -1339,7 +1340,7 @@ export class DomPainter {
     } else {
       // Use configured page gap for normal vertical rendering
       mount.style.gap = `${this.pageGap}px`;
-      if (!this.currentLayout || this.pageStates.length === 0) {
+      if (!previousLayout || this.pageStates.length === 0) {
         this.fullRender(resolvedLayout);
       } else {
         this.patchLayout(resolvedLayout);
@@ -2561,22 +2562,26 @@ export class DomPainter {
   }
 
   private getEffectivePageStyles(): PageStyles | undefined {
+    const documentBackgroundColor = this.currentLayout?.documentBackground?.color;
+    const base = this.options.pageStyles ?? {};
+    const baseWithDocumentBackground = documentBackgroundColor
+      ? { ...base, background: documentBackgroundColor }
+      : base;
+
     if (this.isSemanticFlow) {
-      const base = this.options.pageStyles ?? {};
       return {
-        ...base,
-        background: base.background ?? 'var(--sd-layout-page-bg, #fff)',
+        ...baseWithDocumentBackground,
+        background: baseWithDocumentBackground.background ?? 'var(--sd-layout-page-bg, #fff)',
         boxShadow: 'none',
         border: 'none',
         margin: '0',
       };
     }
     if (this.virtualEnabled && this.layoutMode === 'vertical') {
       // Remove top/bottom margins to avoid double-counting with container gap during virtualization
-      const base = this.options.pageStyles ?? {};
-      return { ...base, margin: '0 auto' };
+      return { ...baseWithDocumentBackground, margin: '0 auto' };
     }
-    return this.options.pageStyles;
+    return documentBackgroundColor ? baseWithDocumentBackground : this.options.pageStyles;
   }
 
   private renderFragment(

packages/super-editor/src/editors/v1/core/presentation-editor/PresentationEditor.ts

@@ -192,6 +192,7 @@ import type {
   SectionMetadata,
   TrackedChangesMode,
   Fragment,
+  DocumentBackground,
 } from '@superdoc/contracts';
 import { extractHeaderFooterSpace as _extractHeaderFooterSpace } from '@superdoc/contracts';
 // TrackChangesBasePluginKey is used by #syncTrackedChangesPreferences and getTrackChangesPluginState.
@@ -502,6 +503,7 @@ export class PresentationEditor extends EventEmitter {
   /** Scroll-isolating wrapper around #hiddenHost. Append/remove this from the DOM. */
   #hiddenHostWrapper: HTMLElement;
   #layoutOptions: LayoutEngineOptions;
+  #configuredDocumentBackground: DocumentBackground | undefined;
   #layoutState: LayoutState = { blocks: [], measures: [], layout: null, bookmarks: new Map() };
   #layoutLookupBlocks: FlowBlock[] = [];
   #layoutLookupMeasures: Measure[] = [];
@@ -702,6 +704,9 @@ export class PresentationEditor extends EventEmitter {
 
     const requestedFlowMode = options.layoutEngineOptions?.flowMode === 'semantic' ? 'semantic' : 'paginated';
     const requestedLayoutMode = options.layoutEngineOptions?.layoutMode ?? 'vertical';
+    this.#configuredDocumentBackground = this.#coerceDocumentBackground(
+      options.layoutEngineOptions?.documentBackground,
+    );
     this.#layoutOptions = {
       pageSize: options.layoutEngineOptions?.pageSize ?? DEFAULT_PAGE_SIZE,
       margins: options.layoutEngineOptions?.margins ?? DEFAULT_MARGINS,
@@ -713,6 +718,7 @@ export class PresentationEditor extends EventEmitter {
             }
           : options.layoutEngineOptions?.virtualization,
       zoom: options.layoutEngineOptions?.zoom ?? 1,
+      ...(this.#configuredDocumentBackground ? { documentBackground: this.#configuredDocumentBackground } : {}),
       pageStyles: options.layoutEngineOptions?.pageStyles,
       debugLabel: options.layoutEngineOptions?.debugLabel,
       layoutMode: requestedFlowMode === 'semantic' ? 'vertical' : requestedLayoutMode,
@@ -7861,6 +7867,12 @@ export class PresentationEditor extends EventEmitter {
     this.#layoutOptions.pageSize = pageSize;
     this.#layoutOptions.margins = margins;
     const flowMode = this.#layoutOptions.flowMode ?? 'paginated';
+    const documentBackground = this.#resolveDocumentBackground();
+    if (documentBackground) {
+      this.#layoutOptions.documentBackground = documentBackground;
+    } else {
+      delete this.#layoutOptions.documentBackground;
+    }
 
     const resolvedMargins = {
       top: margins.top!,
@@ -7900,17 +7912,18 @@ export class PresentationEditor extends EventEmitter {
           marginBottom: semanticMargins.bottom,
         },
         sectionMetadata,
+        ...(documentBackground ? { documentBackground } : {}),
       };
     }
 
     this.#hiddenHost.style.width = `${pageSize.w}px`;
 
     const alternateHeaders = this.#resolveAlternateHeadersFlag();
-
     return {
       flowMode: 'paginated',
       pageSize,
       margins: resolvedMargins,
+      ...(documentBackground ? { documentBackground } : {}),
       ...(columns ? { columns } : {}),
       sectionMetadata,
       alternateHeaders,
@@ -7938,6 +7951,19 @@ export class PresentationEditor extends EventEmitter {
     return out;
   }
 
+  #coerceDocumentBackground(candidate: unknown): DocumentBackground | undefined {
+    if (!candidate || typeof candidate !== 'object') return undefined;
+    const color = (candidate as { color?: unknown }).color;
+    return typeof color === 'string' && color.length > 0 ? { color } : undefined;
+  }
+
+  #resolveDocumentBackground(): DocumentBackground | undefined {
+    return (
+      this.#coerceDocumentBackground(this.#editor?.state?.doc?.attrs?.documentBackground) ??
+      (this.#configuredDocumentBackground ? { ...this.#configuredDocumentBackground } : undefined)
+    );
+  }
+
   #buildHeaderFooterInput() {
     if (this.#isSemanticFlowMode()) {
       return null;